Yv. Orlovskii et al., Nonradiative relaxation and inhomogeneous splitting of aggregated optical centers in the Nd3+-doped CaF2 and SrF2 crystals (FLN and decay study), J LUMINESC, 83-4, 1999, pp. 361-366
Site-selective fluorescence and laser excitation spectroscopy for different
types of optical centers in SrF2 : Nd3 + (0.3 - 1.0%) and SrF2 : La3 + (1.
0%) : Nd3 + (0.2%) were performed at 4.2 K. The crystal-field levels of the
I-4(9/2), F-4(3/2), and (4)G(5/2) multiplets for different Nd3 + optical c
enters were determined in SrF2 : Nd3 + (0.3%). An attempt was made to ident
ify some of the new optical centers on the basis of their fluorescence life
times and crystal-field splitting. Some models of these centers have been d
iscussed. Two-six times reduction of the F-4(3/2) multiplet lifetime was ob
served in the pair M-center in comparison with the single optical centers d
ue to energy cross-relaxation in the pair. A fine splitting of the levels a
t the I-4(9/2)(1)-->(4)G(5/2)(1) crystal-field transition (1.5 cm(-1)) simi
lar to that in CaF2 (2.4 cm(-1)) was found for the Nd-Nd pair in SrF2. The
variation of the splitting from CaF2 to SrF2 nicely demonstrates the R-5 de
pendence of coherent quadrupole-quadrupole interaction. (C) 1999 Elsevier S
cience B.V. All rights reserved.